The present invention relates to damping vibrations between first and second components. More particularly, the invention relates to a permanent magnet damper configured to dampen vibrations transmitted to an elevator car from guide rails on which the car rides.
A typical elevator system includes an elevator car and a counterweight, each suspended on distal points on hoist ropes in an elevator hoistway. In some systems, the elevator car is attached to a car frame to which the hoist ropes are attached. The elevator system also includes guide rails extending the length of the hoistway and attached to opposite sides of the hoistway. A group of roller guides are attached to the elevator car or car frame and guide the car or frame up and down the hoistway along the guide rails.
There are several factors that impact the quality of the elevator car ride in elevator systems. One such factor is the total length of the hoistway. Longer hoistways require a greater number of guide rail segments stacked within the hoistway and a greater number of joints between the guide rail segments. A greater number of guide rail segments results in greater total weight of the guide rails. The increased weight of the guide rail segments causes the rails to deflect in the hoistway. Also, the joints between the guide rail segments result in discontinuities at the joints. Even slightly deflected rails and minimal discontinuity in joints cause an ascending or descending elevator car to vibrate and move laterally.
To minimize the adverse impact of rail imperfections on the ride quality of the elevator car, roller guide assemblies commonly include a suspension system and a damping system. However, prior roller guide assemblies have struggled with balancing the stiffness required for damping and the cushion required for suspension. In addition to roller guide suspension and damping, prior elevator systems have commonly employed crude rubber bumpers arranged between, for example, the frame and the car to steady the car during operation. These bumpers are often mounted and adjusted incorrectly, leading to increased vibration in the elevator car. The material properties of the bumpers degrade over time and therefore necessitate relatively frequent replacement. Finally, the bumpers transmit vibrations, for example from the car frame to the car, which excites other components thereby generating additional noise in the system.
Prior elevator systems have also employed electromagnetic couplers to reduce the impact of guide rail imperfections on the ride quality of the elevator car. However, electromagnetic couplers have several disadvantages. Electromagnetic couplers are subject to failure when the power source driving the electromagnets included in such couplers fails. Electromagnetic couplers consume extra electric energy during operation and increase the mass added to elevator systems employing such couplers. In addition, electromagnetic couplers are very costly, practically prohibiting their use in commercial elevator systems applications.
In addition to active solutions such as the electromagnetic coupler, elevator systems including passive non-contacting permanent magnet couplers have been proposed. One such coupler is described in PCT International Application No. US2007/002433, entitled “Permanent Magnet Noise Isolator.” Non-contacting magnetic couplers, such as described in PCT US2007/002433, may be employed to physically isolate the elevator car from vibrations caused by guide rail imperfections. The magnetic couplers include groups of repelling magnet pairs arranged to form a coupling between, for example, the elevator car and the car frame or the car frame and the roller guides.
In light of the foregoing, the present invention aims to resolve one or more of the aforementioned issues that afflict elevator systems.